Ink-jet receivers are generally classified in one of two categories according to whether the principal component material forms a layer that is “porous” or “non-porous” in nature. Many commercial photo-quality porous receivers are made using a relatively low level of a polymeric binder to lightly bind inorganic particles together to create a network of interstitial pores which absorb ink by capillary action. These receivers can appear to dry immediately after printing and consequently are often the preferred technology as the speed and quantity of ink applied increases. A common problem with such porous receivers is how to achieve a glossy, crack-free receiving layer whilst having minimal effect on puddling and coalescence and yet maintaining good image quality. This is particularly difficult to achieve when a non resin-coated support such as plain paper is utilised to produce a reduced cost receiver.
Much effort has gone into trying to provide ink-jet receivers having improved performance and appearance.
U.S. Pat. No. 6,037,050 (Saito et al) describes an ink-jet recording sheet having a void layer with high ink-absorption with a minimum amount of solid fine particles dispersed in a hydrophilic binder which is cross-linked with a hardener. It discloses, for example, an ink-jet receiver prepared by coating an dispersion of fine silica particles (0.07 μm), PVA, surfactant and sodium tetraborate onto a paper support and allowing the coated support to dry. The dry thickness of the void layer is up to 50 μm and the weight ratio of hydrophilic binder to fine inorganic particles is stated to be within the range of from 1:15 to 1:1.
US-A-2004/0115369 (Yoshida et al) describes an inkjet recording element where an image-recording layer on a support such as paper comprises a pigment, especially alumina, and a binder such as PVA. A treatment solution comprising both boric acid and a borate is applied to the image-recording layer coated on the support, in its wet state, to solidify the binder in the image recording layer. The receiver, while still wet, is then pressed in contact with a heated mirror surface to impart gloss.
U.S. Pat. No. 4,877,686 (Riou et al) describes a method intended to eliminate quality defects associated with the size, shape and uniformity of dots formed through ink-jet printing and in particular to address the blurred appearance arising from large dots with heterogeneous density and extremely irregular shapes of small dots arising from hair cracks in the receiving layer, by using coagulating and gelling products in combination with polyhydroxylic polymeric binders to produce an ink-jet recording sheet which absorbs ink homogeneously and uniformly. It discloses, for example, an ink-jet receiver comprising a relatively porous, absorbent base paper coated with a 5% solution of borax providing a laydown of 0.4 g/m2 and then coated with a 10% solids aqueous dispersion of fine powdered silica, powdered aluminium silicate having a mean diameter of 2.5 μm and polyvinyl alcohol, in a weight ratio of 70:30:30. There is no disclosure of using the borax to increase the surface gloss of the receiver.
U.S. Pat. No. 6,419,987 (Bauer et al) describes a method for increasing the viscosity of a film-forming polymer coating on a moving web to allow higher coating rates and reduced defects in the manufacture of, for example, ink-jet media, by pre-coating a viscosity increasing agent in a first solution and drying prior to coating a second solution containing the film forming polymer. It discloses, for example, an ink-jet receiver prepared by coating a solution of borax and PVP at a dry laydown of 0.11 g/m2 and 0.012 g/m2 respectively onto a PET support and then drying prior to simultaneously coating a two-layer receiving layer comprising a 10% solids solution of PVA and a mordant in a ratio of 75/25 by weight as a base layer and a 5% solids combination of fumed alumina and PVA in a 90/10 ratio by weight as an overcoat layer. There is no disclosure of there being any effect on the gloss of the receiver.
Achieving sufficient gloss whilst maintaining a high ink-absorption rate and good image properties is particularly problematic in porous ink-jet receivers comprising high proportions of inorganic particulate materials when the ink-receiving layer is coated onto non resin-coated support.